FIG. 1 shows a schematic view of a general electric heat pump type air conditioning device. In this system, an electric motor is housed within a closed receptacle for driving the compressor. According to this type, when a deteriorated oil remains in refrigerant pipes or containers, insulation function may be damaged due to moisture or liquid remains in the deteriorated oil. In order to avoid such possible damages, the refrigerant pipes and containers are cleaned upon renewal construction of the heat pump.
FIG. 2 shows a schematic view of a general gas heat pump type air conditioning device. According to this type, different from the electric heat pump type, the compressor is of open type and is separately located from the gas engine (power source). Since this open and independent type structure would not damage any insulation, no cleaning process is needed upon renewal construction of the gas heat pump. For example, pipes and containers are not cleaned when the internal or outdoor unit is exchanged but using existing piping.
According to a patent document 1 (Japanese patent publication No. 3402686), a strainer is proposed which is suitable to be incorporated into a refrigerant recirculation circuit of an air conditioning device. This strainer is formed by a mesh type cage structure and is disposed in the refrigerant piping to catch any foreign materials flowing in the piping.
According to a patent document 2 (Japanese Patent Application publication No. 2001-46811), a filter is proposed which is suitable for filtering a high viscous fluid such as polymer liquid (acetyl-cellulose, acrylic liquid or polyester). This filter is formed with a cylindrical shape having a leading portion at one end thereof and a plurality of cylindrical filter members with different cross sectional sizes provided in pile on the common centerline. Each one end of the cylindrical filter member is detachably connected at one end of an adjacent inner side filter member and each the other end of the cylindrical filtering member is detachably connected to the other end of an adjacent outer side filter member.
When the strainer or filtering member according to the one disclosed in the patent document 1 is used for the air conditioning device, foreign materials may stuck on the mesh cage to reduce the effective refrigerant passing area, which may increase the pressure loss to eventually reduce the cooling function of the air conditioning device. Particularly, when sludge, which is composed by mixed foreign materials such as, remained deteriorated oil and oxidized film in the piping, is generated, the mesh portion of the strainer may be covered with such sludge to greatly reduce the refrigerant passing area.
The filter used in the patent document 2 has a complex structure as explained above and a big pressure loss is expected because of such complex structure if a mesh type is used for filtering.
A need thus exists for a strainer for the air conditioning device that can effectively catch the sludge or foreign materials passing through the piping to prevent or reduce the pressure loss.